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Environmental fate & pathways

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The adsorption and desorption characteristics of acrylic acid to five soils, a loamy sand, a clay loam, two loams and an aquatic sediment, were determined in a guideline study according to EPA guidelines - CFR 40 section 796.2750 and GLP regulations. Acrylic acid was weakly adsorbed onto the soils and sediment. As related to the carbon content of the individual soils, the average Koc for the adsorption step was 42.8 ± 53.98. This places acrylic acid in a high to very high mobility class for adsorption to soils. Thus, the potential for adsorption to soil, sediment, and suspended solids is low.

 

The Henry's Law constant can be calculated by validated Q(SAR) such as EPI Suite v3.20. Henry's Law Constant was calculated to be 0.029 Pa*m3/mol indicating that acrylic acid is essentially not volatile. Due to its pKa value of 4.0, the dissociated anionic form of acrylic acid is dominating under normal environmental conditions (pH range 5.5-9) as calculated by SPARC v4.2 (BASF SE 2009). Therefore, it has to be expected that the real partition of the total acrylic acid is determined only by its anionic form with a Henry's law constant being much lower than calculated above..

 

Distribution modelling using Mackay Level I indicates that acrylic acid is likely to partition to the water compartment (98.7 %) with the remainder partitioning into air (1.3 %); negligible amounts are predicted to occur in other environmental compartments (soil, sediment) (Level I Fugacity, 2009).

 

Based on the physical chemical properties of acrylic acid, the hydrosphere is the main target compartment for distribution and only small amounts will partition in the atmosphere and geosphere.